For the past two years we have employed a non-invasive rebreathing method to obtain values for lung tissue water content (Vtiss) and shown that the method can be used to assess the response of the lung to minor levels of oxygen-induced injury. Using a dog model we plan to assess early stages of acute respiratory insufficiency caused by a wide spectrum of clinically appropriate etiologies: prolonged general anesthesia; fluid overload with both crystalloid and colloid infusions; unilateral acid aspiration; unilateral pulmonary embolisation and unilateral oleic-acid induced pulmonary edema. The concept behind these groups of proposed studies is to assault, in minor degree, both sides of the alveolar-capillary membrane in turn, to determine quantitative responses to different injury-etiologies. In anesthetised animals we plan to use a basic model employing standard methods for measuring cardio-pulmonary variables, with repeated on-line estimations of Vtiss. At the end of each study the animals will be sacrificed to obtain direct measurement of lung tissue water by standard wet/dry weight differences. In normal human volunteers we plan to continue expanding our data-base of values for lung tissue water content into a wider age range, particularly in the 45-65 year range. Due to other committments Dr. Lennart Fagraeus will not continue to be supported by this grant. His place on the team has been taken by Dr. William McIntyre. Several papers are currently in preparation reporting the work carried out in the past year.